1. Field of the Invention
The present invention relates to a cylindrical retainer for mounting a cutting bit to a cutting tool bit mount.
2. Description of the Prior Art
Bits that are used in mining and for removing road surfaces are typically mounted in a machine having a power driven cutter wheel. The wheel has an array of cutter bits mounted on the rim which attack the material to be broken. Each bit desirably includes a hard insert typically made of a carbide material.
One example of such a bit is described in U.S. Pat. No. 4,497,520 to Randell W. Ojanen. In this patent, a rotatable bit 11 is provided as depicted in FIG. 1. Such a bit includes a head portion 13 and a depending shank portion 15. The head portion 13 and shank 15 are coaxially aligned with the head 13 having an enlarged section 17 which prevents the head 13 from being forced into the opening in the mounting block 19. A hard insert 23 typically made of a carbide material is fixedly secured to the forward end of the head 13. The shank portion 15 which is a cylindrical configuration includes a split sleeve 21. The split sleeve 21 is an open ended generally cylindrical-type member through which the shank 15 extends, the sleeve being held in place between an enlarged section 17 and by an enlarged end portion of the shank. When the bit 11 is mounted to the mounting block 19, split sleeve 21 is radially contracted when present in the opening in the mounting block so as to hold the bit 11 in the block 19.
Another example is described in U.S. Pat. No. 4,201,421 to Leroy E. Den Besten et al. In this patent a split tubular open ended spring sleeve 4 is located on the shank 7 of the cutting bit 3 and resiliently engages the inner surface of sockets 10 to secure the bit to the mount 2 in such a manner as to allow the bit to rotate.
In the Ojanen and Den Besten et al patents an enlarged end portion of the shank extends from an open end of the split sleeve bit retainer to hold the retainer in place. In such structure the split sleeve bit retainer covers less than the entire length of the shank of the bit. Accordingly, as the bit rotates the split sleeve provides protection from wear for less than the entire length of the bore into which the shank and retainer are inserted. In addition, since the sleeve is split ease of rotation of the bit is less than optimum since there is less than 360.degree. coverage of the bore. Further, in those instances as in the Ojanen patent wherein the bore into which the shank is inserted extends entirely through the mounting block there is a tendency for foreign material to enter the rear of the bore. The introduction of such foreign matter will have an adverse affect on the wear and rotation of the shank.
It is desirable that a bit retainer be provided which covers the entire length of the shank of the bit so that as the bit rotates during use the retainer provides protection form wear for the entire length of the bore into which the shank and retainer are inserted.
It is also desirable that a bit retainer be provided wherein there is 360.degree. coverage of the bore into which the shank and retainer are inserted so that ease of rotation of the bit is optimized.
It is further desirable in those instances where the mounting bore is a through bore to provide a bit retainer wherein foreign material is prevented from entering the rear of the bore into which the shank and retainer are inserted.